This invention relates to surgical devices and procedures in general. More particularly, this invention relates to bone cement plugs of the sort used in conjunction with bone cement dispensers to compact bone cement into bone canals during joint replacement surgeries.
Bone cement plugs are well known in the art. Such devices are generally used in conjunction with bone cement dispensers to compact bone cement into a bone canal before fixing a prosthetic device in that bone canal. By way of example, bone cement plugs are commonly used in conjunction with bone cement dispensers to compact bone cement into the medullary canal of a femur before fixing the femoral stem of an artificial hip in that canal.
More particularly, in joint replacement surgeries, such as total hip and shoulder replacements, bone cement is commonly used to fix the stem of a prosthetic device in the medullary canal of a bone of the joint. In this respect, it has generally been found that a prosthetic device will be more securely fixed in a bone canal if the bone cement is well packed into the bone canal before the stem of the prosthetic device is positioned in the bone canal.
To this end, after initial preparation and cleaning of the bone canal, the distal portion of the canal is generally occluded with a bone cement plug. The bone cement plug limits uncontrolled flow of bone cement into the distal portion of the bone canal. Ideally, the bone cement plug limits the column of bone cement to about 1 to 2 cm beyond the distal tip of the stem of the prosthesis. After the bone cement plug has been set at the distal portion of the bone canal, bone cement is injected into the distal-most part of the occluded bone canal, adjacent to the plug, using a bone cement dispenser having a long nozzle. The bone canal is then filled with bone cement in a retrograde fashion, by withdrawing the nozzle of the bone cement dispenser from the distal end of the bone canal toward the proximal end of the bone canal as the cement issues from the nozzle. Retrograde filling helps to avoid trapping air in the distal-most part of the bone canal.
After the bone canal has been filled with bone cement, a bone canal pressurizer is connected to the bone cement dispenser. The pressurizer is pressed against the open end of the bone so as to occlude the proximal end of the bone canal. Then more cement is injected into the bone canal, through the pressurizer, under pressure. Under such pressurization, the cement in the bone canal intrudes into the interstices of the inner surface of the bone wall defining the bone canal. When the bone cement sets, a micro-interlock is established between the cement and the irregularities of the inner surface of the bone wall. This significantly enhances fixation of the prosthetic device in the bone canal.
A variety of bone cement plugs are known in the art.
See, for example, the bone cement plugs described and illustrated in U.S. Pat. Nos. 4,245,359; 4,276,659; 4,293,962; 4,302,855; 4,344,190; 4,447,915; 4,627,434; 4,686,973; 4,697,584; 4,745,914; 4,936,859; 4,950,295; 4,994,085; 5,061,287; 5,078,746; 5,092,891; 5,376,120; and 5,383,932.
See also, for example, the bone cement plug described and illustrated in British Patent Document No. 2,253,564A.
See also, for example, the publication entitled xe2x80x9cPolyethylene medullary plug according to Stuhmer/Weberxe2x80x9d distributed by ALLO PRO AG of Switzerland.
See also related apparatus described and illustrated in U.S. Pat. Nos. 4,011,602; 4,523,587; and 4,904,267.
See also related apparatus described and illustrated in European Patent Document No. 0,006,408 B1; and PCT Patent Document No. WO 94/15544.
Unfortunately, all of the bone cement plugs developed to date tend to suffer from one or more significant disadvantages. For example, in general, fixation of the bone cement plug depends on the friction established between the wall of the bone canal and the bone cement plug. Currently, the most common surgical technique is to first measure the size of the prepared bone canal. This typically involves sequentially inserting a number of different xe2x80x9csizersxe2x80x9d into the bone canal so as to determine the gross cross-sectional diameter of the canal at the desired depth. Having thus determined the size of the bone canal, an over-sized plug is inserted into the canal so as to occlude the bone canal at the desired depth.
If the bone cement plug is not sufficiently over-sized relative to the diameter of the bone canal, or if the plug is too easily deformable, the engagement of the bone cement plug with the wall of the bone canal will be less than optimal, which may lead to complications. For example, during the aforementioned pressurization phase, or during the subsequent insertion of the prosthesis, increased pressure of the bone cement can cause the insufficiently-anchored plug to migrate distally.
On the other hand, if the bone cement plug is too greatly over-sized, and/or if the plug is overly rigid, the bone cement plug cannot be inserted into the bone canal to the desired depth. Also, excessively forceful insertion of the bone cement plug into the bone canal can cause the wall of the bone canal to fracture in some circumstances.
In the past, people have traditionally attempted to address these problems by providing plugs in a variety of different sizes for the surgeon to choose from. Unfortunately, this increases the cost of manufacturing the plugs and also increases the cost of inventory.
The foregoing demonstrates the need for a novel bone cement plug that may be adapted to fit any size bone canal. Ideally, a bone cement plug should be easy to deploy at the desired depth in the bone canal and effective in closing off that bone canal. The bone cement plug must also be bio-compatible with the patient. Furthermore, the bone cement plug should be inexpensive to produce.
These and other objects are addressed by the present invention, which comprises a novel device and method for use during joint replacement surgery, such as total hip replacement surgery. The present invention provides a universal bone cement plug which is appropriate for use in any size bone canal. The universal bone cement plug comprises a plurality of detachable units with flanges of decreasing diameter. The invention also provides an insertion tool for deploying the bone cement plug in a bone canal, and a cradle for storing the plug and insertion tool.
The bone cement plug is easy to deploy and align at a desired depth in a bone canal. The rigid, but deformable, plug occludes the bone canal and retains cement in the cavity so defined. The plug is bio-compatible with the patient.
A bone cement plug formed in accordance with the present invention includes a body defined by a series of separable units. Each unit has one or more flexible flanges. Preferably the flanges are slit at their periphery. The flanges decrease in size from the proximal end of the body to the distal end of the body. The largest flange accommodates the largest bone canal reasonably expected to be encountered during surgery. For smaller bone canals in which the largest flange would not fit, appropriate units of the plug may be removed, thus eliminating the oversized flanges in favor of the more appropriately sized flanges.
A first embodiment of the bone cement plug facilitates separating of the units by cutting the body, preferably with the aid of a notch or score line in the body.
A second embodiment of the bone cement plug facilitates separating of the units by tearing the body, preferably with the aid of a notch or score line in the body.
A third embodiment of the bone cement plug facilitates separating of the units by disengaging a fastening mechanism located between adjacent separable units.
Whether whole or truncated, the body of the bone cement plug presents an interface which is engageable by the insertion tool, such that the bone cement plug may be releasably attached to the insertion tool.
The insertion tool facilitates deploying the bone cement plug at a desired depth in the bone canal. An insertion tool formed in accordance with the present invention provides a handle for grasping by the surgeon, a shaft, and a distal end that releasably engages the slug.
The cradle stores the bone cement plug and the insertion tool prior to use. The cradle also provides firm support for the plug should a surgeon need to cut down the plug prior to deploying it in a bone canal. A cradle formed in accordance with the present invention includes a base with an anvil mounted thereon for receiving the plug. At least one set of fingers is preferably mounted on the base for retaining the insertion tool.